Composite Articles and Methods

ABSTRACT

An article comprises: a substrate having a matrix and a plurality of metallic members partially embedded in the matrix; and a metallic layer bonded to exposed portions of the metallic members.

BACKGROUND

The disclosure relates to gas turbine engines. More particularly, the disclosure relates to cold section components in gas turbine engines and nacelles.

In an exemplary gas turbine engine, there are many low temperature components (e.g. service temperatures less than 400 F (200 C)) which may be made of low temperature alloys (e.g., aluminum alloys, composites, molded polymer, or combinations thereof. One example of such a component is a fan strut. One exemplary baseline strut involves metal or composite shrouds adhesively bonded to inner and outer ends or a graphite-epoxy composite with a bonded metallic leading edge. Separately, various metallic-non-metallic combination components have been proposed for use in engines or other areas. U.S. Pat. No. 8,273,430 discloses a duct formed of a metallic inner layer and a polymeric outer layer via a stamping process. Other situations include those found in U.S. Pat. Nos. 4,774,122, 5,535,980, and 6,812,275, US Patent Publication No. 2010/0304065A1, and EP Patent Publication No. 0657267A2.

SUMMARY

One aspect of the disclosure involves an article comprising: a substrate having a matrix and a plurality of metallic members partially embedded in the matrix; and a metallic layer bonded to exposed portions of the metallic members.

In various further embodiments of the foregoing embodiments, the matrix is a thermoplastic material forming a majority of the substrate by weight.

In various further embodiments of the foregoing embodiments, the matrix is a matrix (e.g., resin) of a composite material, the composite material further comprising non-metallic fibers, the matrix and the non-metallic fibers forming a majority of the substrate by weight.

In various further embodiments of the foregoing embodiments, the metallic members comprise fibers.

In various further embodiments of the foregoing embodiments, the exposed portions protrude from a surface of the matrix.

In various further embodiments of the foregoing embodiments, the metallic layer comprises a plated nickel or nickel alloy.

In various further embodiments of the foregoing embodiments, the metallic layer has a thickness of 0.001 inch to 0.020 inch (0.025 mm to 0.51 mm).

In various further embodiments of the foregoing embodiments, the article further comprises one or more additional layers selected from the group consisting of: ceramics; metallic materials; and elastomeric materials.

In various further embodiments of the foregoing embodiments, the article is a strut.

In various further embodiments of the foregoing embodiments, the article is an airfoil element.

In various further embodiments of the foregoing embodiments, the article is a vane or strut having: a platform; a shroud; and the airfoil extending between the platform and the shroud.

In various further embodiments of the foregoing embodiments, a method for manufacturing the article comprises: providing the substrate with the metallic members embedded therein; and processing the substrate to expose or further expose the metallic members.

In various further embodiments of the foregoing embodiments, the method further comprises: after the processing, applying the metallic layer.

In various further embodiments of the foregoing embodiments, the method further comprises: after applying the metallic layer, applying one or more further layers.

In various further embodiments of the foregoing embodiments, the applying one or more further layers comprises applying one or more of: ceramics; metallic materials; and elastomeric materials.

In various further embodiments of the foregoing embodiments, the method further comprises initially forming the substrate by injection molding or transfer molding or thermo-forming or composite layup.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic axial sectional view of a gas turbine engine.

FIG. 2 is a schematic view of a vane.

FIG. 3 is a schematic sectional view of the vane.

FIG. 3A is an enlarged view of a surface region of the article of FIG. 3.

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG. 1 shows a gas turbine engine 20 having an engine case 22 surrounding a centerline or central longitudinal axis 500. An exemplary gas turbine engine is a turbofan engine having a fan section 24 including a fan 26 within a fan case 28. The exemplary engine includes an inlet 30 at an upstream end of the fan case receiving an inlet flow along an inlet flowpath 520. The fan 26 has one or more stages of fan blades 32. Downstream of the fan blades, the flowpath 520 splits into an inboard portion 522 being a core flowpath and passing through a core of the engine and an outboard portion 524 being a bypass flowpath exiting an outlet 34 of the fan case.

The core flow path 522 proceeds downstream to an engine outlet 36 through one or more compressor sections, a combustor, and one or more turbine sections. The exemplary engine has two axial compressor sections and two axial turbine sections, although other configurations are equally applicable. From upstream to downstream there is a low pressure compressor section (LPC) 40, a high pressure compressor section (HPC) 42, a combustor section 44, a high pressure turbine section (HPT) 46, and a low pressure turbine section (LPT) 48. Each of the LPC, HPC, HPT, and LPT comprises one or more stages of blades which may be interspersed with one or more stages of stator vanes.

In the exemplary engine, the blade stages of the LPC and LPT are part of a low pressure spool mounted for rotation about the axis 500. The exemplary low pressure spool includes a shaft (low pressure shaft) 50 which couples the blade stages of the LPT to those of the LPC and allows the LPT to drive rotation of the LPC. In the exemplary engine, the shaft 50 also directly drives the fan. In alternative implementations, the fan may be driven via a transmission (e.g., a fan gear drive system such as an epicyclic transmission between the fan and the low pressure spool) to allow the fan to rotate at a lower speed than the low pressure shaft. Also, although shown as an axial two-spool engine, other spool counts and configurations may be used.

The exemplary engine further includes a high pressure shaft 52 mounted for rotation about the axis 500 and coupling the blade stages of the HPT to those of the HPC to allow the HPT to drive rotation of the HPC. In the combustor 44, fuel is introduced to compressed air from the HPC and combusted to produce a high pressure gas which, in turn, is expanded in the turbine sections to extract energy and drive rotation of the respective turbine sections and their associated compressor sections (to provide the compressed air to the combustor) and fan.

One or more components of the engine (articles) may be manufactured as a metallic-polymer composite. The composite may replace a baseline component formed of wrought or cast aluminum alloy, steel, or titanium alloy. The exemplary articles are outside of the hot section of the engine. For example, if along the core flow path, they may be in the LPC section or upstream thereof. Examples include fan struts or fan exit guide vanes and LPC vanes.

FIG. 2 shows an exemplary strut 60 comprising an inboard platform 62, an outboard shroud 64, and an airfoil 66 extending between the platform and shroud. The airfoil has a pressure side 68, suction side 70, leading edge 72 and trailing edge 74.

The exemplary platform has an outboard (gas path-facing) surface 76 and the shroud has an inboard (gas path-facing) surface 78.

The platform has an inboard surface 80 and the shroud has an outboard surface 82 which may bear mounting features for mounting to additional components. For example, when implemented as a fan strut, the shroud outboard surface may mate to a fan nacelle structure and the platform inboard surface may mate to a case structure of the engine core.

For another example, when implemented as an LPC vane, the shroud may contain mounting features for mounting to the case and the platform may contain mounting features for mounting to seals, and the like. The circumferential array of the vanes may form a vane stage of the LPC. The platform and shroud may each have perimeter portions 84 and/or 86 of which the lateral surface portions may bear seals or other features for interfacing with adjacent segments. The exemplary operating temperatures of the LPC vanes and other “cold” components are up to 350° F. (177° C.).

The strut or vane 60 comprises a substrate (FIG. 3) 120 and a coating 122. In a minimal example of the reengineering from an exemplary composite strut with metallic leading edge, the substrate is a substrate of the airfoil and the platform and shroud are separately manufactured (metallic or composite) and adhered to the airfoil.

The coating may include one or more layers. The layers include at least a metallic layer 124. One or more functional layers 126 atop the metal layer may be of appropriate materials for functions such as wear resistance, heat resistance, environmental protection, and the like. At least along a surface layer 128 of the substrate, the substrate includes at least partially embedded metallic members 130 (FIG. 3A) in a matrix 132. At least some of these members protrude from a surface 134 of the matrix so as to have a respective embedded portion 136 and exposed/protruding portion 138. The portions 138 are thus in contact with the metallic layer 124 and structurally interlock the metallic layer to the matrix and thus to the substrate.

Exemplary members 130 are metal strands or fibers (e.g., having transverse dimensions less than 1 mm, more narrowly, less than 0.5 mm or 4-25 micrometers or 5-7 micrometers. Exemplary member lengths are substantially in excess of the transverse dimensions (e.g., diameters for circular sections). For example, exemplary lengths are at least three times a transverse dimension (more narrowly, at least five times or 3-20 times or 4-10 times). As is discussed further below, they may be even greater such as at least 50 times.

FIG. 3A also shows an exemplary substrate depth or thickness as T_(S); an exemplary metallic layer thickness between an inboard surface 140 and an outboard surface 142 as T_(M); and an exemplary functional layer thickness between an inboard surface 144 and an outboard surface 146 as T_(F). Exemplary T_(S) is substantially in excess of T_(M) and T_(F) (e.g., at least 10 times greater, more particularly, at least 50 times greater or at least 100 times greater). Exemplary T_(M) is 0.001 inch to 0.020 inch (0.025 mm to 0.51 mm), more narrowly, 0.05 mm to 0.4 mm. Exemplary T_(F) will depend upon the nature of the particular functional coating material or materials, if any. In a variety of applications, this may be between an exemplary 0.01 mm and 1.0 mm, more narrowly, 0.02 mm-0.5 mm.

Several different processes may be used for manufacturing the substrate. The substrate may be molded having an essentially uniform distribution of the members. Alternatively, the distribution may be concentrated at or near a substrate surface by means such as two-shot molding or by pre-lining the surfaces of the mold with the members. The metallic members may be formed as woven wires (either a purely woven tape or other form or with some amount of metal wires interwoven with non-metallic fibers/strands). In such cases the metal member length to transverse dimensions could (at least initially) be very high such as at least 50:1 or near infinite. Such a tape, sheet, or other material could form the last (or first) layer in a lay-up operation. This may involve known composite techniques involving non-metallic fibers (e.g., aramid fiber, carbon fiber, and the like) in a matrix (e.g., epoxy or other resin). Various lay-up techniques involve carbon or other fiber fabric sheets, tapes, tows, and the like.

Yet other possibilities involve molding or lay-up of the substrate without the members and then somehow partially embedding the members (e.g., via melting into the substrate surface).

In situations where initial exposure of the members is insufficient, member exposure may be increased by preferential removal of matrix material (i.e., removing matrix material disproportionately to removal (if any) of the adjacent metal members such as via preferential chemical attack on the matrix or abrasion). Exemplary methods include abrasive blast, burnishing, acid etching, plasma etch, acid gas, and the like or combinations. Some of these may not rupture long metallic strands (e.g., a preferential chemical attack on matrix material might generally expose non-terminal portions of long metallic strands initially included in a composite tape.

The metallic layer may then be applied via techniques such as electroplating or electroless plating. Thereafter, the additional layers may be applied. In the particular example, the substrate is a suitable engineering thermoplastic such as nylon, polyetherimide, polyamideimide, polytetheretherketone and the like. The metal members may be stainless steel, titanium or titanium alloy or nickel or nickel alloy introduced by compounding directly into the thermoplastic. The metal layer is nickel or nickel alloy or other suitable alloys applied by electrolytic or electroless plating techniques. The additional layers may be ceramic, metallic or elastomeric applied by various techniques such as plasma, flame spray, cathodic arc, plating and solution coating processes. For example the additional layers may be: ceramics such as zirconia, yttria stablized zirconia, alumina, hafnia, and the like and metallics deposited by methods such as but not limited to cathodic arc spray, plasma spray, flame spray. Other non-metallic, non ceramic, coatings may be polyurethanes, fluorosilicones, silicones, fluorocarbons, and/or perfluorocarbons applied by spray, dipping, painting, or the like.

Relative to a baseline metallic component, the composite component may offer manufacturing cost (and time) advantages and/or weight advantages. For example, the basic molding process may be less expensive than a more complicated machining process.

Relative to a baseline non-metallic (e.g., purely polymeric or carbon fiber composite) component or even a plated non-metallic component, advantages would be expected to include a greater bond strength of a metal layer (if any) relative to the polymer (of bulk polymer or matrix). This may result in increased durability, stiffness, thermal resistance, erosion resistance, and the like (any or all of which may be traded off for a weight reduction).

Relative to other hybrids such as a composite airfoil with a bonded machined (or electroformed) metallic leading edge strip, there may also be weight and manufacturing cost savings.

Among other candidate components are: fan blades; compressor airfoils such as blades and vanes; air bleed duct components; bifurcation ducts; and thrust reverser cascades and blocker doors in the nacelle (and subcomponents of any of these such as where such component includes a plated nonmetallic substrate/matrix as a body portion and metallic fittings, etc.).

One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when implemented as a replacement for a baseline part, details of the baseline may influence details of any particular implementation. Accordingly, other embodiments are within the scope of the following claims. 

What is claimed is:
 1. An article comprising: a substrate having a matrix and a plurality of metallic members partially embedded in the matrix; and a metallic layer bonded to exposed portions of the metallic members.
 2. The article of claim 1 wherein: the matrix is a thermoplastic material forming a majority of the substrate by weight.
 3. The article of claim 1 wherein: the matrix is a matrix of a composite material, the composite material further comprising non-metallic fibers, the matrix and the non-metallic fibers forming a majority of the substrate by weight.
 4. The article of claim 1 wherein: the metallic members comprise fibers.
 5. The article of claim 1 wherein: the exposed portions protrude from a surface of the matrix.
 6. The article of claim 1 wherein: the metallic layer comprises a plated nickel or nickel alloy.
 7. The article of claim 1 wherein: the metallic layer has a thickness of 0.001 inch to 0.020 inch (0.025 mm to 0.51 mm).
 8. The article of claim 1 further comprising: one or more additional layers selected from the group consisting of: ceramics; metallic materials; and elastomeric materials.
 9. The article of claim 1 being a duct.
 10. The article of claim 1 being a strut.
 11. The article of claim 1 being an airfoil element.
 12. The article of claim 11 being a blade.
 13. The article of claim 11 being a vane or strut having: a platform; a shroud; and the airfoil extending between the platform and the shroud.
 14. A method for manufacturing the article of claim 1, the method comprising: providing the substrate with the metallic members embedded therein; and processing the substrate to expose or further expose the metallic members.
 15. The method of claim 14 further comprising: after the processing, applying the metallic layer.
 16. The method of claim 15 further comprising: after applying the metallic layer, applying one or more further layers.
 17. The method of claim 16 wherein: the applying one or more further layers comprises applying one or more of: ceramics; metallic materials; and elastomeric materials.
 18. The method of claim 14 further comprising: initially forming the substrate by: injection molding.
 19. The method of claim 14 further comprising: initially forming the substrate by: transfer molding or thermo-forming.
 20. The method of claim 14 further comprising: initially forming the substrate by: composite layup. 